is attenuation accounted for

Hi
Does anyone know if when I set a light to rgb 100 100 100 radiance takes into
account the attenuation over distance? I'm trying to write a ray-tracer but the
colour values returned for a reflected ray are about 100 times too high.
Thanks

Tarik

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Tarik Rahman
PhD student, Institue of Perception, Action and Behaviour
School of Informatics
University of Edinburgh

Hi Tarik,

Rays reflected off a mirror-like finish (polished glass, mirrors, etc.) do not attenuate with distance, but their chances of striking a light source are small. Rays that are part of the "direct" calculation and sent to light sources to test for shadows account for the 1/r^2 fall-off of light by computing the solid angle of the source (or source sample region) in their equation. For details, see Section 4 of the following document:

  http://radsite.lbl.gov/radiance/refer/materials.pdf

I'm sure you can find similar advice in books like "An Introduction to Ray Tracing," by Glassner.

-Greg

···

From: Tarik Rahman <[email protected]>
Date: July 21, 2004 7:56:10 AM PDT

Hi
Does anyone know if when I set a light to rgb 100 100 100 radiance takes into
account the attenuation over distance? I'm trying to write a ray-tracer but the
colour values returned for a reflected ray are about 100 times too high.
Thanks

Tarik

--
Tarik Rahman
PhD student, Institue of Perception, Action and Behaviour
School of Informatics
University of Edinburgh